Liquid food and beverage preparation machines have been known for a number of years. For example, U.S. Pat. No. 5,943,472 discloses a water circulation system between a water reservoir and a hot water or vapor distribution chamber of an espresso machine. The circulation system includes a valve, metallic heating tube and pump that are connected together and to the reservoir via different silicone hoses, which are joined using clamping collars.
EP 1 646 305 discloses a beverage preparation machine with a heating device that heats circulating water which is then supplied to the inlet of a brewing unit. The brewing unit is arranged to pass heated water to a capsule containing a beverage ingredient for its brewing. The brewing unit has a chamber delimited by a first part and a second part movable relative to the first part and a guide for positioning a capsule in an intermediate position between the first and second parts before moving the first and second parts together from an open to a closed configuration of the brewing unit.
In-line heaters for heating circulating liquid, in particular water are also well known and are for example disclosed in CH 593 044, DE 74 33 407, DE 103 22 034, DE 197 32 414, DE 197 37 694, EP 0 353 425, EP 0 485 211, EP 1 380 243, FR 1 299 354, FR 2 799 630, U.S. Pat. No. 4,242,568, U.S. Pat. No. 4,595,131, U.S. Pat. No. 5,019,690, U.S. Pat. No. 5,392,694, U.S. Pat. No. 5,862,738, U.S. Pat. No. 5,943,472, U.S. Pat. No. 6,393,967, U.S. Pat. No. 6,889,598, U.S. Pat. No. 7,286,752, WO 00/11914, WO 01/54551, WO 2004/006742 and WO2004/062443.
For instance, FR 1 299 354 discloses a single in-line water heater device that can be integrated in different apparatus requiring different heating powers. The heater device has several heating resistors which are connected to the power circuit of such an apparatus and the terminals of which are insulated and extend outside the device for connection. To set the appropriate heating power of the heater, the terminals of the different resistors are so connected to the power circuit of the apparatus to provide a serial, parallel, star or delta configuration of the resistors of the heater device, whereby the heating power of the heater device is adjusted to the power needed by the apparatus. GB 607,297 discloses a system allowing a selection by a user of a particular heating power from a group of predetermined heating power levels for a heating apparatus, such as a heater or a heating plate or a cooker. In this case, the heating apparatus includes several heating resistors that are electrically connected in a serial or parallel configuration by means of a combination connector device between the heating apparatus and the electric distributor circuit. The combination connector device comprises: a base assembly fixed on the wall adjacent to the heating apparatus and connected to the distributor circuit; and a plug assembly connected to the resistors of the heating apparatus. The plug assembly has three pins connected to the resistors. The base assembly has a series of sockets onto which the plug may be connected. Each socket has a different inter-connection so as to provide a different serial or parallel configuration of the resistors when the plug is connected to the socket. Hence, moving the plug along the base from one socket to another changes the resistor configuration of the heating apparatus and thus the heating power thereof when the socket assembly is connected to the electric distributor circuit.
A fine adjustment of the heating power is disclosed in WO 01/54551. This document discloses an in-line heater having a permanently powered first heating resistor for pre-heating water circulating in the heater and a second heating resistor that is automatically switched on and off as required for adjusting the temperature of the pre-heated water to reach a target temperature. Similarly, EP 1 380 243 discloses an in-line heater with three resistors and three switches that are so interconnected to provide various serial, parallel and mixed resistor configurations switchable automatically to allow fine adjustment of the heating power generated by the resistors and adjust precisely the temperature of the heated water.
One problem encountered with the conception of beverage machines relates to the different domestic voltage levels used in different places and countries. For example, domestic nominal base voltages in different places are generally: 220-230 VAC in Europe and China and Argentina, 120 VAC in the US, between 110 and 220 VAC depending on the area in Brazil and Colombia, 100 VAC in Japan, 240 VAC in Australia and Kuwait, etc. . . . Hence, a beverage machine must either be dedicated for a single electric power supply area or must include a means to adapt to the different domestic voltage supply of different areas.
For example, U.S. Pat. No. 5,862,738 discloses a beverage preparation machine that is arranged for including one of two separated heater elements, namely a first heater element that can be operated with 115 VAC and a second heater element that can be operated with 230 VAC. This requires the switching of the heater elements when the power supply is changed.
EP 0 353 425 discloses a heater for a beverage machine that has two heating resistors and a switch so inter-connected together that the resistors may be switched from a parallel into a serial configuration and vice versa by operating the switch. Hence, by switching the resistor configuration, the heater is adapted for a 110 and 220 V, providing the switching is done properly to fit the characteristics of the power source. DE 74 33 407 discloses a coffee machine with a similar resistor configuration that may be switched. FR 1 289 545 discloses a similar system for a soldering iron in which the user-switch for switching between the parallel and serial resistor configurations is incorporated in the plug of the device's power cord. In all these cases, the user may select a proper switch configuration to adjust the device to the power source. This, of course, involves the risk of improper user-configuration and safety risks or at least malfunction of the devices in case of improper powering thereof.
A solution to this problem has been proposed in WO 00/11914. This application discloses a direct electrical heater having a pair of electrodes with a power supply for passing an electric heating current between the electrodes via the liquid circulated in a beverage machine. The heater includes a power supplier connectable to the mains which provides 120-480 V having a frequency of 50-60 Hz at 10-75 Amp. The heating rate is proportional to the power supply and thus depends on the voltage of the mains. The power supply may though be controlled by a variable switch for limiting the percentage of time of current supply. To minimise the flickering effect the power supply includes, in series, an AC/DC converter, a voltage level controller and a DC/AC converter, the voltage level controller being adjustable to control the voltage that is then supplied to the electrodes via the DC/AC converter. Such double conversion systems are quite expensive and lead also to significant power loss in the conversion.
WO 2004/062443 discloses a beverage preparation apparatus having a power circuit that can be used with different types of external supply voltages, domestic or foreign. The power circuit includes a heater that is directly coupled via an on/off switch to the foreign or domestic voltage supply in the range of 88 to 264 V at a frequency of 47-63 Hz. The apparatus also has a power supply, mounted in parallel with the heater, that converts the voltage supply into 5, 12, 24 or 30 VDC for powering a controller, a pump, a display and lights of the apparatus. The controller is arranged to send control signals for controlling the operating of the power circuit via the on/off switch.
A problem with this latter arrangement lies in the fact that the heater of the power circuit will be over-dimensioned or under-dimensioned depending on the type of electric supply. For higher voltage supply, e.g., 240 V, this will lead to excessive switching, to reduce the length of the powering periods of the heater during a heating cycle, and high power peaks during the powering periods with the resulting risk of inadmissible flickering and/or electromagnetic interference (EMI), inadmissibly high instantaneous current consumption and/or inadmissibly large temperature variations of the water. For lower voltage supply, the heater will not be able to generate enough heat for heating larger quantities of water.